Acid Test- How to Spot Minerals Separately

What is an Acid Test?

An acid test is a chemical or metallurgical process in which acids are used to find out what kind of material is in a sample of rock or mineral.

Examples of Acid Tests

The acid test shows which rocks have minerals made of carbonate. In this method, a drop of watered-down (5-10%) hydrochloric acid is put on a rock or mineral and bubbles of carbon dioxide gas are looked for. The bubbles show that the rock or mineral contains carbonate minerals.

For the gold test, an acid test is also used. When a gold-colored object is rubbed on a black stone, it leaves a mark that can be seen. This mark is tested by adding aqua fortis (nitric acid), which dissolves the mark of all gold-colored objects except gold. When tested with aqua regia, which is a mixture of nitric acid and hydrochloric acid in a ratio of 1:3, the remaining mark dissolves.

Let’s see what happens to minerals when acid is put on them.

Apparatus And Ingredients Required To Perform The Test

Here are the tools and materials you’ll need to do the acid test to separate the minerals.

1. The mineral sample set viz. lodestone, azurite, rose quartz, amethyst, calcite, pyrite, talc (8 Nos).
2. Vinegar (one bottle).
3. Steel nail
4. Paper and Pencil
5. Magnifying glass
6. Eyedropper
7. Paper towel
8. Cup(Non-reactive metal)

How To Perform The Experiment

Let’s talk about the different steps that need to be taken in order to use the acid test to find the different minerals. Here are eight steps to help you try things out.

Step 1: Write words like “Fizz,” “Sample,” and “Powder” in each column on the piece of paper.

Step 2: Write the names of the mineral samples, such as pyrite, calcite, etc., on the left side of the paper where it says “Samples.”

Step 3: Pour a little vinegar into the cup. Vinegar usually has between 5 and 8% acetic acid by volume, which you can take with an eyedropper later.

Step 4: Put the mineral sample you chose on the paper towel and use the eyedropper to put a drop of vinegar (an acid drop) on it.

Step 5: Look closely at the mineral and see how the chemical reaction works, like how vinegar fizzing is a result of the reaction. If it is, write “Yes” in the fizz column. If not, write “No.”

Step 6: If the vinegar didn’t fizz as expected, scratch the mineral sample with a steel nail. If there is no effect on the mineral, write “too hard” under the column for “powder.” If the scratch causes the mineral powder to come out, put a drop of vinegar on the powder.

Step 7: Use the magnifying glass to see if the mineral is fizzing or not. Write “yes” or “no” under the powder column, depending on the answer.

Step 8: Do the same thing with every other sample of mineral.

Results of the acid test

First, let’s look at the results of calcium carbonate-containing minerals. These minerals will fizz the first time you try to use them. If there are minerals that have calcium carbonate as their main component and have close molecular bonds, they need to be ground into a powder to see if they are different. This is one of the easiest ways to tell the difference between these minerals.

When acid hits carbonate minerals, it makes them unstable. When acid starts to bubble on a sample, a reaction similar to the one below is happening.

CaCO3 + CH3COOH → Ca(CH3COO)2 + H2O + CO2

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